This invention relates to a tread mill, particularly to an improved speed-adjusting mechanism for a tread mill which includes a V-belt drive transmission mechanism having a laterally movable transmission shaft to adjust the speed of the transmission.
The parent application of this application discloses a tread mill with a speed-adjusting mechanism and a slope-adjusting mechanism. The speed-adjusting mechanism includes two V-belt carrying pulleys, i.e., two pairs of cone-shaped discs mounted coaxially on a transmission shaft which is provided between an output shaft of a motor and a driven shaft associated with the tread belt. One of the pairs of the discs has a fixed disc and a slideable disc which is adjacent to the slideable disc of the other pair of discs, and the slideable discs slide mutually upon displacement of the transmission shaft. A V-belt is passed over one pair of the discs and a pulley mounted on the output shaft, and another V-belt is passed over the other pair of the discs and a pulley mounted on the shaft of the rotative tread belt. An arrangement for displacing the transmission shaft is provided for adjusting the transmission speed. This arrangement is rather complicated.